1. Field of the Invention
The present invention relates to a method of fabricating an electron-emitting device, a method of fabricating an electron source and a method of fabricating an image-forming apparatus that uses the electron source.
2. Related Background Art
Among electron-emitting devices, a surface conduction electron-emitting device utilizes a phenomenon in which electron emission is caused by flowing an electric current to a thin film formed with a small area on a substrate and in parallel to the film surface. JP 07-235255 A discloses a surface conduction electron-emitting device that uses a metal thin film made of Pd or the like. FIGS. 1A and 1B schematically show a configuration of the device. In the figures, reference numeral 1 denotes a substrate. Reference numeral 4 denotes an electroconductive film consisting of a metal oxide thin film or the like made of Pd or the like. The electroconductive film 4 is locally destroyed, deformed or denatured by an energization operation called energization forming that will be discussed below to form a gap 5 that is kept in a state of electrically high resistance.
The surface conduction electron-emitting device that was subject to the energization forming operation emits electrons from the above-described gap 5 by a voltage being applied on both the ends of the electroconductive film 4 and an electric current being flown to the device.
Moreover, in order to improve an electron-emitting characteristic, the surface conduction electron-emitting device may be subject to an operation called xe2x80x9cactivationxe2x80x9d as will be discussed below to form a film (carbon film) consisting of carbon/carbon compound in the above-described gap 5 and in its vicinity. This step can be performed by a method of applying a pulse voltage to the device in an atmosphere containing an organic material to cause the carbon/carbon compound to deposit around the gap 5 (EP-A-660357, JP 07-192614 A, JP 07-235255 A and JP 08-07749 A).
The above-described surface conduction electron-emitting device has an advantage in that a number of devices can be arranged and formed over a large area since it is simple in its structure and is easily fabricated. Therefore, its application to a charged beam source, a display apparatus and the like has been studied.
As an example of arranging and forming a lot of surface conduction electron-emitting devices, there is an electron source in which surface conduction electron-emitting devices are arranged in parallel with each other and multiple rows formed by connecting both ends of each of the devices by wirings (common wirings), respectively, are arranged (e.g., JP 64-031332 A, JP 01-283749 A, JP 02-257552 A and the like).
As an example of a display apparatus, there is an image-forming apparatus in which an electron source having a lot of surface conduction electron-emitting devices arranged therein and a phosphor for emitting visible light by an electron emitted from this electron source are combined (e.g., U.S. Pat. No. 5,066,883 B).
In such an image-forming apparatus, some contrivances have been made in steps of forming and activation in order to secure uniformity of a displayed image, and a measure for judging an end of an activation step based on electric characteristics in the activation step is also taken (e.g., JP 09-6399 A).
In addition, as an electron-emitting device other than the above-described surface conduction electron-emitting device, there is a field emission type electron-emitting device (FE: Field Emitter). As an example of this FE, there is a Spindt type FE, which is a micro-cold cathode constituted by a microscopic conical emitter and a control electrode (gate electrode) formed near the emitter and having a function of drawing out an electric current from the emitter and an electric current control function. A cold cathode in which the Spindt type FEs are arranged in an array shape is proposed by C. A. Spindt et al. (C. A. Spindt, A Thin-Film Field-Emission Cathode, Journal of Applied Physics, Vol. 39, No. 7, pp. 3504, 1968). In recent years, in the field of such an FE, a technique is disclosed which applies a voltage to a part between a gate electrode and a cathode electrode connected to the emitter in an atmosphere containing an organic material, thereby causing a carbon compound to deposit on the surface of the emitter to improve an electron-emitting efficiency (JP 10-50206 A).
As an electron source substrate on which a lot of electron-emitting devices are formed, for example, there is an electron source substrate of a passive matrix configuration in which electron-emitting devices are arranged in a matrix shape over N rows and M columns. When the above-described activation step for causing carbon or carbon compound to deposit is applied to such an electron source substrate, a voltage is applied to a common wiring of N rows and M columns, which is connected to a device electrode, by, for example, the following methods. These methods are described in JP 09-134666 A and EP-A-726591.
(1) Applying a voltage line by line from first row to Nth row in order.
(2) Scroll activation for partitioning N rows into a few blocks to sequentially apply a phase-shifted pulse to each block.
However, in both the cases of the above methods (1) and (2), when the number of devices increases, time required for the activation step becomes longer. In addition, if the number of blocks into which N rows are partitioned as in the method (2) is reduced, a duty of a voltage applied to one row falls to slow down an activation and cause drop in an amount of electron emission and an electron-emitting efficiency, whereby a satisfactory electron-emitting device is not obtained.
Thus, it has been attempted to reduce activation time by increasing the number of lines to which a voltage is simultaneously applied. However, the activation step for causing carbon and carbon compound to deposit in an electron-emitting region and in its vicinity is performed by decomposing an organic material adsorbed onto an electron source substrate from the atmosphere. Thus, when the number of devices to which the activation step is simultaneously applied increases, an amount of the organic material to be decomposed and reacted on the electron source substrate per unit time also increases. As a result, a concentration of the organic material in the atmosphere fluctuates, formation of a carbon film is slowed down or a carbon film is formed in a different speed according to positions on the surface of the electron source substrate, whereby uniformity of an obtained electron source is deteriorated.
The present invention has been devised in view of the above-described drawbacks, and it is an object of the present invention to provide a method of fabricating an electron-emitting device and an electron source that are capable of performing an activation step in shorter time.
In addition, it is another object of the present invention to provide a method of fabricating an electron-emitting device and an electron source that are capable of forming a film of carbon or carbon compound excellent in crystallinity during an activation step in shorter time.
In addition, it is another object of the present invention to provide a method of fabricating an electron source that is capable of performing an activation step in shorter time even in fabrication of an electron source provided with a plurality of electron-emitting devices.
In addition, it is another object of the present invention to provide a method of fabricating an electron source that is capable of fabricating an electron source provided with an electron-emitting device excellent in uniformity in an activation step in shorter time even in fabrication of an electron source provided with a plurality of electron-emitting devices.
Further, it is yet another object of the present invention to provide a method of fabricating an image-forming apparatus that is capable of obtaining an image forming apparatus that can realize a uniform luminance characteristic.
According to one aspect of the present invention, a method of forming a deposit of carbon or carbon compound on a precursory structure which becomes an electron-emitting region in an electron-emitting device made on a substrate, comprises a first step for depositing carbon or carbon compound in a gas atmosphere which includes a carbon compound of a first molecular weight, and subsequently a second step for depositing carbon or carbon compound in a gas atmosphere which includes a carbon compound of a second molecular weight smaller than the first molecular weight.
According to another aspect of the present invention, a method of fabricating an electron-emitting device, comprise a forming step for forming a pair of conductive members which are arranged with a gap and an activation step for depositing carbon or carbon compound on at least one of the conductive members in the pair, wherein the activation step includes at least first and second steps, in the first step the carbon or carbon compound being deposited in a gas atmosphere which includes a carbon compound of a first molecular weight, and in the second step taken succeeding to the first step, the carbon or carbon compound being deposited in a gas atmosphere which includes a carbon compound of a second molecular weight smaller than the first molecular weight.
In the above methods, typically the second step is conducted as the final step in the deposit forming process.
The present invention is a method of fabricating an electron source provided with a plurality of electron-emitting devices and a wiring connected to the plurality of electron-emitting devices on a substrate, wherein the plurality of electron-emitting devices are fabricated by the above-described fabricating method.
In addition, the present invention is a method of fabricating an image-forming apparatus having an electron source and an image-forming member, wherein the electron source is fabricated by the above-described fabricating method.